Description
In the Linux kernel, the following vulnerability has been resolved:
Input: cs40l50-vibra - validate custom data from user space
cs40l50_add() copies the custom data of an FF_PERIODIC/FF_CUSTOM effect
straight from the ff_effect the user passed to EVIOCSFF, without
requiring it to hold anything:
work_data.custom_data = memdup_array_user(periodic->custom_data,
periodic->custom_len,
sizeof(s16));
work_data.custom_len = periodic->custom_len;
The driver then reads two words out of that buffer: custom_data[0] as the
waveform bank in cs40l50_effect_bank_set(), and custom_data[1] as the
index within the bank in cs40l50_effect_index_set(). Neither read is
covered by a length check, and custom_len is fully user controlled:
- custom_len == 0 makes memdup_array_user() call memdup_user() with a
length of zero, which returns ZERO_SIZE_PTR rather than an error, so
custom_data[0] dereferences it.
- custom_len == 1 allocates two bytes. A bank of ROM or RAM keeps
effect->type out of the OWT case, and custom_data[1] is then read one
word past the allocation.
The bank value itself is also mishandled. It is masked with
CS40L50_CUSTOM_DATA_MASK (0xffff) but stored in an s16, so a
custom_data[0] of 0x8000 or above wraps to a negative value that passes
the "bank_type >= CS40L50_WVFRM_BANK_NUM" test.
cs40l50_effect_index_set() indexes vib->dsp.banks[] with it before the
switch statement's default case gets a chance to reject it:
base_index = vib->dsp.banks[effect->type].base_index;
max_index = vib->dsp.banks[effect->type].max_index;
Require the two words the driver reads to be present, and hold the masked
bank in a u32 so the existing upper-bound test covers the whole range.
The da7280 haptic driver already range checks custom_len this way.
Références
